Filtrate Quality Research Articles

Study of different pretreatments for reverse osmosis reclamation of a petrochemical secondary effluent

Conventionally treated petrochemical wastewaters contain substantial quantities of hazardous pollutants. In addition, wastewater reuse is being enhanced as a consequence of the shortage of fresh water. Advanced petrochemical wastewater treatment for water reuse will reduce hazardous pollutants discharges as well as water consumption. Reverse osmosis is a suitable technology to obtain pure water. This work studies the adequacy of different pretreatments applied to a petrochemical secondary effluent to produce a suitable feeding for reverse osmosis treatment. The permeate obtained can be used in the petrochemical industry for different processes. In this work, several experiments (granulated activated carbon filtration, ultrafiltration, nanofiltration and granulated activated carbon filtration coupled with nanofiltration) were performed to improve the conventional pretreatment. Total organic carbon, chemical oxygen demand, turbidity and silt density index were used to evaluate water quality for reverse osmosis feeding. In granulated activated carbon filtration, all the measured parameters but silt density index indicated a good filtrate quality to feed reverse osmosis membranes. Although the ultrafiltration permeate obtained was suitable for reverse osmosis, nanofiltration and granulated activated carbon filtration coupled with NF provided a better effluent quality for reverse osmosis than the other pretreatments studied.

Plasma and cryoprecipitate manufactured from whole blood held overnight at room temperature meet quality standards

With buffy coat (BC) processing of whole blood (WB) donations, the preparation of plasma occurs within 24 hours rather than 8 hours of collection. The effect of this change on coagulation factor function in plasma and cryoprecipitate was evaluated during the validation of this production method and with routine production. Plasma frozen after an overnight hold of WB was prepared via BC or whole blood filtration (WBF) methods and quality control (QC) variables were measured. Additionally, plasma prepared with the BC method was compared to plasma produced using the platelet-rich plasma (PRP) method with an extended plasma factor analysis. Selected plasma factor levels were also measured in both cryoprecipitate and cryosupernatant plasma prepared using the WBF method from plasma frozen on the day of collection or after an overnight hold of WB. When comparing BC plasma to PRP plasma, coagulation factors (F)II, VII, VIII, IX, X, and XI had somewhat lower levels, and fibrinogen and antithrombin levels were elevated. As expected the most sensitive to the prolongation of production time was FVIII with 72 and 78% of the activity of PRP plasma and cryoprecipitate, respectively. However, both still met QC standards. Similarly, products made in routine production show acceptable levels of FVIII. Plasma and cryoprecipitate products, prepared using methods in which the plasma is frozen close to 24 hours after collection, meet current quality standards. The longer WB storage time has been implemented into general use in Canada.

Effect of shading on performance of slow sand filters

This research investigated the effect of shading on three slow sand filters, each 1.65 m in diameter. One filter (designated “sun”) served as the control and was open to the sun and sky, the second filter (designated “shaded”) was partly shaded to exclude direct sunlight, and the third (designated “covered”) was completely shaded. All three filters were operated at filtration rates of 0.1 and 0.2 m/h using the same influent raw water. Research was conducted in the summer season when algal activity is at its peak. The performance of the filters was assessed on the basis of filtrate quality and length of filter run. Statistical evaluation of the physicochemical quality of filtrate was performed. Quantitative estimation was made of phytoplankton and zooplankton in the raw and filtered waters. Results indicated that in a tropical country, shading of slow sand filters may help reduce the algal activity in the filters without materially affecting the filter performance.

Biofilter as pretreatment to membrane based desalination: Evaluation in terms of fouling index

The removal of particulate matter and dissolved organic matter from seawater by the use of biofiltration was investigated. Granular activated carbon (GAC) and anthracite were used as biofilter media at two different filtration velocities. Filtrate quality was measured in terms of silt density index (SDI), modified fouling index (MFI) and turbidity removal. Reverse osmosis (RO) was used as a post-treatment. Both biofilters demonstrated similar fouling reduction behavior in terms of SDI and MFI. Fouling potential in terms of MFI values decreased to 10 s/L 2 within the first 10–15 days of operation and kept constant up to the remaining experimental period of 55 days of operation for both GAC and anthracite biofilter. The filtrate turbidity was steady after 10 days and remained low at a value of 0.2–0.3 NTU and 0.28–0.31 NTU for anthracite and GAC biofilter, respectively. Furthermore, the headloss development was low and within 20 cm for biofilter operated at a low velocity of 5 m/h. A post-treatment of reverse osmosis after a pretreatment of GAC and anthracite biofilters showed a reduction in normalized flux decline ( J/ J 0) from 0.22 to 0.12 and 0.35 to 0.21 during the first 20 h, respectively. The RO flux for seawater declined at a faster rate and continued even after 3 days when no pretreatment was provided.

The safety analysis of living-related kidney donors in short term after transplantation

To evaluate the safety of living related donors in short term after transplantation. Two hundred and fifty-one cases of living related donor kidney transplantation from May 2000 to July 2007 were analysed retrospectively. There were 117 male and 134 female aged from 22 to 72 years old, with a mean of 46.6 years old. The indexes were compared including serum creatinine (SCr), creatinine clearance (CCr), glomerular filtration rate (GFR) and quality of life before and after donation. Surgical complications were followed-up. Donors' SCr was (75.9 +/- 17.2) micromol/L before donation, (107.4 +/- 21.2) micromol/L on 7 d after donation, (130.4 +/- 58.2) micromol/L at the 1(st) month and (116.1 +/- 24.1) micromol/L at the 3(rd) month. There were significant difference between any 2 time points (P < 0.01). CCr was (94.4 +/- 17.5) ml/min before donation and (63.5 +/- 17.8) ml/min on 10 d after donation (P < 0.01). In 62 donors, total GFR was (82.4 +/- 21.8) ml/min before donation. On 10 d after donation, GFR of remaining kidney was (57.4 +/- 14.1) ml/min which was 34.7% higher than GFR of this kidney before donation (42.6 +/- 11.8) ml/min. There was no significant difference in quality of life before living related donors and non-donor populations (P = 0.116). Surgical complications included splenic rupture in 1 case, descending colon rupture in 1 case and wound infection in 5 cases. Living donor kidney transplantation is safe for donors, although part of indexes would vary within normal range during the early time after donation.

Peculiarities of filtering continuous messages in the signal space with algebraic grid properties

Algorithm of filtering narrowband signal on the noise background under their interference in the signal space with algebraic grid properties is considered. Filtration quality factors for a device which realizes this processing algorithm are obtained. It is shown that significantly better filtration quality factors may be achieved in the signal space with algebraic grid properties compared to the linear one.

Influence of operating conditions on the efficiency of domestic wastewater treatment in membrane bioreactors

This paper quantifies the influence of operating conditions on the efficiency of domestic wastewater treatment and of membrane bioreactors (MBR) performance with a statistical method (multivariate linear regression model). The impact of the following seven parameters—(1) transmembrane pressure (TMP), (2) mixed liquor suspended solids (MLSS), (3) dissolved oxygen concentration (DO), (4) hydraulic retention time (HRT), (5) sludge retention time (SRT), (6) temperature (T) and (7) pH on the accumulated filtrate volume (V) and water quality (COD, NH 3-N) —were investigated. The results showed that MLSS and temperature had 34% and about 23% respectively the majority of the influence on the resulting filtrate volume among the seven influencing parameters. The mathematic expression obtained by the multivariate linear regression model between the accumulated filtrate volume and operating conditions was V = 249.64 TMP−0.056 MLSS + 31.69 DO + 55.06 pH−5.25 T−8.82 HRT + 16.24. The COD of the filtrate primarily depended on the process temperature, which carried about 64% of the weight among all the seven investigated parameters. The ammonia nitrogen concentration (NH 3-N), of the effluent was mainly a function of MLSS (about 40% influence) and pH (about 27% influence). No effect of the TMP on the filtrate quality was found. In addition, the mathematic expressions between COD, NH 3-N and operating conditions were COD = 0.0073 MLSS−5.64 DO + 2.86 T + 0.099 SRT + 2.48 HRT−88.82 and NH 3-N = 0.017 MLSS−12.99 DO−28.86 pH + 0.90 T + 0.13 SRT + 201.30. These mathematic expressions could possibly be used to optimize and predict the efficiency of domestic wastewater treatment in bioreactor parameters.

Snowmelt‐induced diel fluxes through the hyporheic zone

Snowmelt processes result in diel fluctuations in streamflow and stream stage that propagate into riparian aquifers and cause a daily pumping of the hyporheic zone. This diel pumping was observed in stream stage and water table records collected in Tuolumne Meadows, Yosemite National Park, California. A model was developed using Fourier analysis to represent the stream stage fluctuations and a solution to the 1‐D, linearized Boussinesq equation for groundwater flow. The modeling demonstrates that a substantial volume of water is pumped in and out of the aquifer via this process on a daily basis. In addition, since the snowmelt‐induced groundwater fluctuations exhibit both reduced amplitudes and increased time lags at distances away from the stream, the model can be used to estimate the hydraulic parameters of the riparian aquifer. Snowmelt‐induced hyporheic pumping may have implications for biogeochemical processes in the hyporheic zone and may provide important ecosystem services related to water filtration, thermal buffering, nutrient cycling, and water quality. Consideration should be given to recognizing, quantifying, and monitoring snowmelt‐induced pumping of the hyporheic zone and the ecosystem services it provides since climate and land use changes may alter the magnitude of this process in the future.

Comparison of an ultrafiltration membrane fed with raw seawater, coagulated seawater and cooling tower blowdown

In order to determine the suitability of an ultrafiltration membrane module (Omexell™ SFP2660) to different feed waters, the filtrate quality and the operation status of the module were studied comparatively when it was fed with raw seawater, coagulated seawater and cooling tower blowdown (CTB) respectively. The results indicated that (1) under a flux of 60–65 L·m −2·h −1, the UF membrane module was suitable for the three kinds of feed water; (2) when fed with the CTB and operated at an increased flux (90 L·m −2·h −1), the module could still keep stable production while the filtrate quality became a little poorer (turbidity ≥0.1 NTU) and the transmembrane resistance went a bit higher (transmembrane pressure, ≥0.15 bar); (3) due to low concentration of organic matter (total organic carbon, <2 mg/L) in the feed water, the residual contamination in the membrane is little; and (4) feed water temperature had a great effect on the silt density index of the filtrate. So the membrane module could not only adapt to the three kinds of feed water, but it also endured the fluctuation of feed water turbidity (7–300 NTU) and flux (60–90 L·m −2·h −1), whereas stabilized and clarified feed water provided by the coagulation process will benefit the membrane module for long-term operation.

The Effect of Ventilation, Filtration and Passive Sorption on Indoor Air Quality in Museum Storage Rooms

A study was conducted in five storage rooms at the National Museum of Denmark, in which the effect on indoor air quality of mechanical ventilation, filtration and passive sorption was investigated. Mechanical ventilation and recirculation/filtration was initiated by introducing new ventilation and filtration units. Passive sorption was initiated by hanging sheets of sorptive materials on walls. The control strategies were evaluated in terms of their ability to lower the concentration of internally generated pollutants, and the indoor-to-outdoor concentration ratio of outdoor pollutants. The overall environmental impact for each method was evaluated by the use of material dosimeters. It was found that passive sorption performed better in a small room compared to a large room. Mechanical ventilation and filtration with activated charcoal gave a high protection against ozone, but were less effective in reducing nitrogen dioxide. Increased ventilation rates were expected to dilute internally generated pollutants, but ambiguous results imply that the emission rate of organic acids may also vary. Recirculation/filtration was generally the most efficient method. A cautious conclusion is that a combination of a low air exchange rate and internal recirculation with filtration will be most beneficial to the indoor air quality for such low-activity storage buildings.

Survival and quality of life after renal angioplasty: a five-year follow-up study

Renal percutaneous transluminal angioplasty (PTA) treatment of renal artery stenosis has been performed worldwide since 1978, but it is still a matter of debate as to what extent the patients benefit from the procedure in terms of quality of life and long-term survival. Of 139 patients referred for renal angioplasty owing to hypertension or pending uraemia, 105 were subsequently treated with PTA. Eighty-eight patients survived for 5 years. Fifty-nine patients were re-examined according to a protocol including physical examination, blood pressure, drug therapy, glomerular filtration rate and quality of life assessment, and an additional 29 patients were interviewed by telephone regarding quality of life. PTA was not conducted in 34 patients owing to high risks as decided at joint radiology-nephrology conferences. The 5-year survival was 83% for PTA-treated patients with arteriosclerotic renovascular disease, 100% for patients with fibromuscular vascular disease and 47% for the non-PTA-treated patients. The main causes of death were cardiovascular and cerebrovascular events in both groups. Reduced blood pressure and reduced need for antihypertensive drug treatment were observed in the PTA-treated patients. The renal function was stable. A majority of the PTA-treated patients stated that they had "unrestricted" physical activity, and the physical, mental and social well-being was self-rated as level 4-5 (mostly good and very good) on a five-grade scale by 53%, 67% and 75% of the patients, respectively, at the follow-up investigation. The untreated patients were not interviewed. The study showed a high survival rate, improved blood pressure control and stable renal function 5 years after renal PTA, and a vast majority of the patients rated their physical, mental and social well-being favourably.

Impact of polyhexamethylene guanidine hydrochloride on the process of coagulation treatment of river waters

The paper has investigated flocculation capacity of polyhexamethylene guanidine hydrochloride during joint treatment with aluminum sulfate of the Dnieper and Desna River water in the spring period. It has been shown that additives 1–5 mg/dm3 of the matter under study during coagulation treatment of the river waters improves the process of their clarification, increases the filtrate quality in terms of main indicators and makes it possible to reduce by 10–20 mg/dm3 the dose of the coagulant. A pronounced flocculation effect manifests itself when treating the waters in question by the doses of a polymer preparation respectively 3–5 and 2–3 mg/dm3. Polyhexamethylene guanidine (without a coagulant) ensures a standardized quality of the filtrate in terms of color and turbidity only when treating weakly stained water of the Desna River. It has been found that ≥ 99% of polyhexamethylene guanidine is retained by the medium of a sand filter.

Equivalent Cake Filtration Model

Cake filtration has been widely used in many chemical processes with more non-Newtonian, highly viscous and compressible materials involved. Neither traditional nor modern filtration theory can be applied in practice. “Equivalent cake filtration model” is a recently developed mathematical model to describe cake filtration for both Newtonian and non-Newtonian fluids, in either steady or unsteady filtration stages. This model has two strengths: (1) It can be used to determine equivalent capillary radii and predict filtration quality based on the properties of solid/liquid system and operation parameters; and (2) to calculate cake specific resistance and its variations with time at various cake thickness locations.

The role of powdered activated carbon in enhancing the performance of membrane systems for water treatment

This study was conducted to investigate the effects of powdered activated carbon (PAC) with immersed flat sheet membrane on the efficiencies of operation and treatment and to evaluate the performance of the system. The experiments were carried out under operating conditions of an average filtration rate of 0.65 m/d, water temperature of 22–26°C, and PAC dose of 0 g/L (System A) and 20 g/L (System B). The regular influent concentrations of total organic carbon (TOC) and UV absorbance at 254 nm (UV 254) were 3.186 mg/L and 1.7 1/m, respectively. TOC removal of 66.2 and 69.8%, and UV 254 removal of 70.6 and 82.4% were obtained from System A and System B, respectively. During an experimental period of 65 days, the value of TMP (trans-membrane pressure) in System B increased by 16 kPa, but the value of TMP in System B reached 61 kPa after 48 days. As a result, continuous filtration time was extended by using PAC. Bacteria count in the reactor of System B showed one hundred times higher than that of System A and most of the bacteria existed in the adsorbed state on the PAC. Higher biological activity can be expected by holding PAC in the filtration reactor. This study revealed that the filtrate quality and the performance efficiency were enhanced when PAC was introduced into the filtration system.

Pretreatment for desalination of seawater from an open intake by dual-media filtration: Pilot testing and comparison of two different media

The results of pilot testing of dual media filtration on seawater from an open intake in the Thermaikos Gulf, northern Greece, are presented in this study. Two different filter materials, FILTRALITE MC, a processed expanded clay material with particle range 1.5–2.5 mm, and anthracite coal with a similar particle range, were tested in parallel operation under various operating conditions (coagulant type and dose, filtration rate). Attention was focused on filtrate quality parameters relevant to feeding RO membrane desalination systems, that is, turbidity, silt density index (SDI), total organic carbon (TOC). In order to evaluate the effect of temperature variations on pretreatment performance, similar experiments were performed during a winter and a summer campaign of the same year. Despite the poor quality of feedwater, through an open intake, very low turbidities and SDI values lower than 5 could be obtained by means of coagulation and dual media filtration. Both filtration materials demonstrated almost similar performance in removing particulates from the feed water and produced permeates of acceptable quality for feeding RO systems (SDI 15 values lower than 5) during the winter and summer campaigns. It was observed that both filters were much more effective during the summer period due to the higher temperatures prevailing, which allowed the formation of larger aggregates and their subsequent effective capture within the filter media. Laboratory and on site pilot tests showed that optimal performance was achieved when polyaluminum chloride (PACl) was added to the feed water as a coagulant medium at a dose 1.8 mg Al/L. In the winter period similar SDI 15values were obtained by both filters when operating at a flow velocity of 10m/h, whereas at 5 m/h the sand/filtralite column produced water with lower SDI 15values and better quality compared to the one from the sand/anthracite column. On the other hand, during the summer period, and for the same coagulant dose, similar SDI 15values (usually close to 3) were obtained by both filters at all the tested flow velocities (5, 10, 15 m/h). Furthermore, due to the effect of temperature on aggregation, in the winter period the duration of filtration cycles was found to be determined by particle breakthrough. In contrast, in the summer no breakthrough was observed and the filtration cycles were determined by the available free space for hydrostatic head buildup above the filter media. Finally, regarding the hydrostatic head development, it was observed that the sand/filtralite column had a slower head buildup than the sand/anthracite column for the same duration of filter operation.

Evaluation of hydrophobicity/oleophilicity of kapok and its performance in oily water filtration: Comparison of raw and solvent-treated fibers

Kapok ( Ceiba pentandra) fiber, an agricultural product, contains waxy material that contributes to its hydrophobic–oleophilic characteristics. Its performances, as untreated and solvent-treated fibers, in deep-bed filtration of oily water containing 2.5% diesel were assessed in this study. The solvents used were ethanol and chloroform. The filtration performance was assessed through measurements of column breakthrough time, filtration rate, filtrate quality, and the amount of oil retained by the filter column at breakthrough under a constant vacuum pressure. The kapok fibers, both at its natural state and after solvent treatments, demonstrated excellent oil/water separation and filtration, for which oil was retained while water was filtered through the kapok filter column. The filtrate quality, in terms of turbidity and percent oil removal, appeared to be unaffected by the solvent treatment of the kapok fiber. The oil removal efficiencies consistently exceeded 99%. However, the filter column packed with solvent-treated kapok fibers showed premature breakthrough of the oily influent and produced less filtrate than that by the untreated kapok. The filter column packed with the solvent-treated kapok also retained less oil compared to the untreated kapok, and as a result, a quarter of the filter pore volume was not wetted even after breakthrough. This could be the main cause for the premature breakthrough of the oily influent. Apparently, the solvent treatment for impurities removal could impair the oleophilicity/hydrophobicity of the kapok fibers which was crucial for the oily water separation and filtration.

Effect of natural coagulant application on microfiltration performance in treatment of secondary oxidation pond effluent

A secondary oxidation pond effluent was treated using hollow-fibre crossflow microfiltration and coagulation process. Preliminary tests were carried out to find the optimum dosage of Moringa oleifera (a natural coagulant) for the coagulation process. Optimum dosage of Moringa oleifera was recorded as 100 mg/L for turbidity of secondary oxidation pond effluents ranging between 30 and 100 NTU. Turbidity removal achieved ranged between 50 and 57%. The performance of microfiltration coupled with coagulation using optimum dosage of Moringa oleifera was investigated. Better flux performance and lower rate of fouling were achieved when combining microfiltration with coagulation. Pseudo-steady state flux of 3 L/m 2.h at a relatively constant suction pressure of less than 0.6 bar was obtained after 300 h of filtration time. Results showed that the values of COD, BOD 5, alkalinity, VSS, TS, turbidity and pH in the filtrate were not influenced significantly by incorporation of coagulation using Moringa oleifera. The filtrate quality of about 50 mg/L COD, 25 mg/L BOD 5, 2 mg CaCO 3/L alkalinity, 1 NTU turbidity, 1 mg/L TSS and VSS respectively was produced when using microfiltration with and without coagulation.

Pilot Tests of Multibore UF Membrane at Addur SWRO Desalination Plant, Bahrain

UF membranes with new Multibore design were tested in a pilot unit at the Addur SWRO Desalination Plant, Bahrain as pre-treatment for RO. The seawater at Addur is known for its extremely bad condition, mainly caused by industrial and residential waste disposals and high organic contents and bioactivity. Feed water for the pilot plant was taken from the Addur seawater supply line (intake 1.2 km offshore, chlorinated) directly, without making use of the existing media filtration. The existing UF/RO plant at Addur is suffering from heavy fouling and scaling problems. The pilot unit was started in March 2003. A first set of trials was done to test different operational modes and cleaning procedures under extreme fouling conditions. Based on these trials new modified UF modules were installed inMarch 2004 and operated until July 2005. During these 16 month of service the newMultibore UF membranes performed successfully. During summer month 2004 no membrane cleaning except normal backwash procedures with sodium hypo chloride was necessary for stable operation. The use of not chlorinated seawater as feed to the UF was tested in October 2004 and during the outage of the Addur plant February-April 2005. This water was taken by a newly installed 3’’ intake pipe from a location about 200 m offshore from a depth of 1.5 m only. This so called ‘‘raw beach water’’ turned out to be not suitable for UF filtration due to its extremely high fouling potential. The injection of flocculants into feedwater was tested to further improve the UF output and filtrate quality. The dosing of very small amounts of Fe proved to be beneficial. During summer 2005 the UF operation with Fe injection was stable with a flux of 70 l/m 2h at a differential pressure around 250 mbar only. Filtrate SDI was always well below 3, even below 2 in July 2005. An additional RO pilot unit was installed inMay 2004 to directly test the fouling potential of the filtrate from the UF pilot plant. In the RO pilot plant a permeator as it is used at the Addur SWRO plant was installed. The fouling of this permeator was remarkably lower compared to the fouling in the Addur SWRO desalination plant. This proves the high quality of the UF filtrate in addition to the low SDI values. Because of the low consumption of cleaning chemicals, low differential pressure and no need for media filtration the operating costs for Multibore UF membranes would be remarkably lower compared to the operating costs of the existing arrangement at Addur. The pilot test under the extreme seawater conditions of Addur revealed that these new UF membranes are a very promising alternative for pre-treatment for SWRO desalination plants.

Enhancing flexible fiber filter (3FM) performance using in-line coagulation

A new packing for deep bed filtration using Flexible Fibers has been proposed and developed on a very large scale for tertiary treatment of wastewater. The purpose of this study is to check the possibility of using this technology for the production of drinking water from surface water. In this study, the feasibility of the fiber filter application on water treatment was examined and the removal efficiency of fiber filter was improved using an in-line coagulant injection method. The experiments were carried out at pilot scale. The filter was packed with bundles of polyamide fibers with a bed porosity of 93%. Nak-dong River was used as the filter influent water and alum, PSOM, and PAC were used as the coagulants. The coagulants were injected by the in-line injection method. Small dosages (1-5 mg/L) of the polymeric coagulants (PSOM and PAC) showed an increase of removal efficiency compared to the operation without coagulants. Specifically, 1 mg/L of PAC showed the longest filtration time. Considering filtration time, filtrate quality, and filtered volume, the filtration velocity of 120 m/hr was chosen as an optimum value. For long-term operations, the effluent quality was 0.4 NTU and the removal efficiency was stable for the given optimum conditions.

Performance and mechanism of a hydrophobic–oleophilic kapok filter for oil/water separation

Abstract A natural vegetable fiber, kapok, was evaluated for its feasibility as filter material for separating immiscible liquids such as oil/water mixtures. Two types of oils, namely diesel and hydraulic, were investigated. Various simulated oily waters were prepared by mixing tap water with one of these oils to produce binary oil/water mixtures of varying oil percentages, such as 5%, 10% and 15% by weight. The effect of filter packing density on the dynamics of oil/water separation during the filtration process and the filtrate quality were investigated. Due to the hydrophobic–oleophilic surface characteristic of the kapok fiber, water could be filtered through the filter while oils were retained, causing separation of oil from water. The filtration efficiency for removal of diesel and hydraulic oil from their respective oily waters reached 100% and more than 99.4%, respectively, which showed an excellent performance of kapok in removing oils from oily waters. The hydraulic conductivity of the kapok filter was found to decrease with the advance of the oil front. The filtration rate of both types of oily waters decreased with increasing filter packing densities and influent oil contents. The kapok filter performed equally well in terms of total filtrate collected before breakthrough for the two different oils, albeit the filtrate rate could be viscosity dependent. A packing density of 0.07 g/cm 3 was the optimum one for diesel and hydraulic oil removal. At breakthrough, the oil/water/air three-phase partition within the filter bed is a function of influent oil concentration, oil type, and packing density of the filter.